This invention relates to a cutting control apparatus for cutting into a set length, by a flying cutter, a sheet, pipe or like material fed by a material feeder, such as a leveler, a pinch roll or the like.
In a conventional flying cutter, the revolving speed of a cutting blade is controlled by a speed change mechanism for cutting length setting use, such as a stepless speed change gear, and a material to be cut is fed at a constant speed. To increase the cutting length of the material, the revolving speed of the blade is reduced to increase the length of the material being fed during one rotation of the cutter; and to reduce the cutting length of the material, the revolving speed of the blade is raised. That is to say, the blade is driven at a constant speed during one rotation, and the length of a material fed during one rotation of the blade is the cutting length of the material, so that to change the cutting length of the material, the revolving speed of the blade must be changed by the abovesaid speed change mechanism. Since such a change in the revolving speed of the blade cannot be made finely, the dimensional accuracy of the cutting operation is low.
In the case where the moving speeds of the blade and the material are not equal to each other when the blade makes contact with the material, the material is sometimes not cut neatly or the blade may be broken. To avoid this, in the prior art, use is made of a blade speed change mechanism, by which during each rotation of the blade, a rocking movement of the blade is added to its ratational movement; consequently, during each rotation the revolving speed of the blade varies about its mean revolving speed. The blade speed change mechanism is adjusted so that the speed of the blade when making contact with the material may be equal to the moving speed of the latter. For example, when it is desired to increase the material cutting length, since the revolving speed of the blade is reduced, as described above, the blade speed change mechanism is adjusted in such a manner that the blade is brought into contact with the material at a speed higher than the mean speed of the blade during one rotation thereof. Since operation for this adjustment is relatively troublesome, however, changing of a set value for cutting often results in markedly lowered cutting efficiency. Further, since the range in which the revolving speed of the blade is adjustable is relatively narrow, the range over which the material cutting length can be altered is also narrow.
An object of this invention is to provide a cutting control apparatus which employs, in place of the conventional speed change mechanism for cutting length setting use, a numerical control servo mechanism to permit easy setting of the cutting length and to provide for enhanced accuracy in the cutting operation, and which employs a blade speed change mechanism, such as employed in the past, to reduce speed changes of a servo motor, whereby to prevent inertia from being an obstacle to high-speed cutting, and which is adapted so that mechanical synchronization setting need not be altered for each small change in the cutting length.
Another object of this invetion is to provide a cutting control apparatus which permits a correct cutting operation even if a synchronous cutting length corresponding to setting of the blade speed change mechanism, for example the set angle of an eccentric gear and the material cutting length, differ from each other.